1. Field of Invention
The present invention relates to a unit for mounting, on a prism, an electro-optical device for modulating a plurality of colored light beams in accordance with image data, and a projector using the unit for mounting an electro-optical device.
2. Description of Related Art
Hitherto, projectors have been used which include an electro-optical device for modulating a plurality of colored light beams in accordance with image data, a cross-dichroic prism for synthesizing the light beams modulated by the electro-optical device, and a projection lens for enlarging and projecting the light beams synthesized by the prism.
Projectors are widely used for multimedia presentations at public meetings, such as conferences, academic meetings, and exhibitions. The projector is brought to the conference room, and is occasionally moved to another place, as needed. Therefore, reduction in size of projectors has progressed.
Recently, the projectors have been reduced in size and have been provided with a structure in which three optical modulators are fixed to side surfaces of a cross-dichroic prism via a fixing material, so as to simplifying the structure. Hereinafter, the structure is called a xe2x80x9cPOP structurexe2x80x9d (panel-on-prism structure).
In the POP structure, electro-optical devices supported by supporting frames are fixed by soldering or via an adhesive to the surfaces of a prism at a predetermined distance from the surfaces of the prism. The inventor of the present application proposed in an unpublished patent application a POP structure in which pins, to which an adhesive is applied, are inserted into holes formed in an electro-optical device at four corner thereof, each pin being fixed to a prism at an end of the pin and to a supporting frame of the electro-optical device at the periphery of the pin (Japanese Patent Application No. 11-25345).
A projector is provided with a light source, a power source, and the like. Certain parts of the projector heat up during use. Therefore, the projector is provided with a cooling fan, an exhaust fan, and the like so that the inside of the projector does not become excessively hot.
The supporting frame of an electro-optical device is generally made of a resin which has a coefficient of thermal expansion higher than that of a prism, which is made of glass. Therefore, when the projector is used, the supporting frame is expanded by the heat more than the prism. Since the supporting frame is mounted via the fixing pins as described above, the expansion of the supporting frame affects the fixing pins and pushes the fixing pins, thereby displacing the supporting frame from the predetermined mounted position. As a result, there is a risk of aberration in picture elements, which would deteriorate the image quality.
Accordingly, an object of the present invention is at least to provide a mounting unit and a projector using the mounting unit in which displacement of an electro-optical device, such as a liquid crystal panel, can be suppressed, the displacement being caused by heat generated when the projector is used.
According to one exemplary embodiment of the present invention, a unit for mounting an electro-optical device may consist of a supporting frame for supporting an electro-optical device, and a fixing pin for fixing the supporting frame for supporting an electro-optical device to a prism. The fixing pin is fixed to the prism at an end of the fixing pin and is fixed to the electro-optical device at an end or intermediate part of the fixing pin, particularly at a side surface thereof. The fixing pin is provided with an absorbing structure for absorbing deformation by heat of the supporting frame.
According to various embodiments of this invention, the absorbing structure can absorb deformation by heat of the supporting frame, whereby, when the supporting frame is expanded by heat, the fixing pin can absorb the effects of the expansion to some extent. Therefore, the electro-optical device, such as a liquid crystal panel, can be prevented from being displaced by heat generated when the projector is used.
The absorbing structure may have different cross-sectional areas depending on sections, thereby providing resiliency. Further, the absorbing structure may use a resilient material for a portion of the fixing pin so as to use deflection of the material, or may be any structure which can absorb the deformation by heat.
According to one exemplary embodiment of the present invention, the fixing pin may be made of one material and the cross-sectional area of the fixing pin may be smaller at least at the intermediate part than at the end thereof fixed to the prism. The absorbing structure is preferably thus formed.
With this arrangement, the structure is simple and can be manufactured easily.
The fixing pin may have greater cross-sectional areas at the ends and a smaller cross-sectional area at an intermediate part of the fixing pin. The cross-sectional areas at the ends of the fixing pin may be different from each other.
According to another exemplary embodiment of the present invention, the following expression is preferably satisfied
(d/D)4xc3x97(1/W)=C
in which D denotes the diameter of the section of the end of the fixing pin to be fixed to the prism, d denotes the diameter of the section of the intermediate part of the fixing pin, W denotes a stress generated by the deformation by heat of the supporting frame, and C denotes a constant.
By considering the above expression, it is possible to calculate the size of the fixing pin according to the material and the size of the supporting frame for supporting the electro-optical device.
According to another exemplary embodiment of the present invention, the supporting frame for supporting an electro-optical device is preferably made of a resin including a carbon fiber.
By using a resin including a carbon fiber, the supporting frame for supporting an electro-optical device can be relatively easily formed which has a coefficient of thermal expansion lower than that which uses a pure resin. Therefore, the stress applied to the fixing pin by thermal expansion of the supporting frame for supporting an electro-optical device can be reduced, whereby deformation by heat of the supporting frame of the electro-optical device can be surely avoided.
The cross-sectional area of the supporting frame for supporting an electro-optical device is preferably 40 mm2 or less.
With this arrangement, the stress applied to the fixing pin by thermal expansion of the supporting frame for supporting an electro-optical device can be reduced, thereby suppressing deformation by heat of the supporting frame of the electro-optical device more reliably.
The above-described unit for mounting an electro-optical device can be used for a projector which may consist of a plurality of electro-optical devices for modulating a plurality of colored light beams in accordance with image data, a prism for synthesizing the light beams modulated by the electro-optical devices, and a projection lens for enlarging and projecting the light beams synthesized by the prism. When the projector is provided with the unit described above for mounting an electro-optical device, the displacement of the electro-optical devices caused by heat during the use of the projector can be avoided, whereby a projector which can maintain a high image quality for a long period is made possible.